1. Field of the Invention
The present invention relates generally to a compressor for compressing a fluid such as air or refrigerant gas, and, more particularly, to a scroll type compressor.
2. Description of the Related Art
Conventional air conditioning systems for vehicles are equipped with compressors, which compress refrigerant gas to permit vaporized refrigerant (refrigerant gas) to be easily liquefied by a condenser. Conventional compressors include piston type compressors, which compress fluid by the reciprocating action of pistons, and vane type compressors, which compress fluid by the rotation of a rotor provided with a vane. Recently, scroll type compressors, which accomplish internal compression with higher efficiency than piston type or vane type compressors, have been put to practical use.
With reference to FIG. 7, the basic structure of a scroll type compressor for use in an ordinary air conditioning system for a vehicle will be described. FIG. 7 is a cross-sectional view of a prior art scroll type compressor as viewed from the front, and shows only a fixed scroll and a movable scroll for simplicity.
The ordinary scroll type compressor comprises a fixed scroll 71, which is secured to an outer wall 77 or the like, and which serves as a non-rotating, and a movable scroll 73, which is coupled to an eccentric shaft (not shown) to rotate. The spiral element 72, of the fixed scroll 71 engages with the spiral element 74 of the movable scroll 73, defining compression chambers 75 between both scrolls 71 and 73. When the eccentric shaft is rotated by a power source like an engine (not shown), the movable scroll 73 makes an orbital movement about the axis of the fixed scroll 71. The compression chambers 75 gradually move toward the center portion from the peripheral side of the spiral element 74, thus accomplishing the gas compression. The outer wall 77 has the shape of a complete round, and the spiral elements 72 and 74 of both scrolls 71 and 73 are formed along involute curves having complete rounds of predetermined radii as reference circles.
However, installing the conventional scroll type compressor into an automobile raises the following problem. Due to the recent progression of electronic controls for vehicles, multiple control components such as actuators and sensors for various controls are installed in the engine compartment of a vehicle. When a compressor for an air conditioning system is mounted on a vehicle, there may be no extra space in the vertical direction of the compressor while there may be some extra space in the widthwise direction of the compressor, or vice versa. It is difficult to secure sufficient space in the engine compartment.
One may think that this shortcoming can be overcome by simply making the compressor compact. However, if the individual scrolls 71 and 73 are made smaller, the compression displacement is reduced, and the cooling performance is lowered.